CN104818410B - Dental is cut processing blank material and metal powder for powder metallurgy - Google Patents

Abstract

Processing blank material is cut the present invention provides dental, metal powder for powder metallurgy, the porcelain metal framework and dental prostheses of dental, wherein, Co is principal component, ratio of the mass ratio below 35% is accounted for account for mass ratio more than 26% and contains Cr, ratio of the mass ratio below 12% is accounted for account for mass ratio more than 5% and contains Mo, ratio of the mass ratio below 2.0% is accounted for account for mass ratio more than 0.3% and contains Si, ratio of the mass ratio below 0.5% is accounted for account for mass ratio more than 0.09% and contains N, the processing that is cut of the dental is made of with blank material the sintered body of metal dust.

Description

Dental blanks for machining and metal powders for powder metallurgy

technical field

The present invention relates to a blank material for cutting in dentistry, a metal powder for powder metallurgy, a metal frame for ceramics in dentistry and a dental prosthesis.

Background technique

In dental treatment, crowns, bridges or dentures are often used to repair crown defects or tooth defects. Among them, from the viewpoints of aesthetics and functionality, dental prostheses in which a ceramic material called pottery is baked on the surface of a metal frame can be used.

Patent Document 1 discloses a precious metal alloy for metal frames in which metal elements such as Sn, Ga, and In are added to metal elements such as Au, Pd, Cu, Ir, and Ag. Since this alloy can be formed into a desired shape by casting, a dental prosthesis with good aesthetics can be obtained by baking a ceramic material for tooth crown restoration on the surface of a metal frame made of this alloy.

On the other hand, recently, a method of measuring the three-dimensional shape of an affected part and forming a metal frame based on the obtained shape data has become widespread. This structure is called a dental CAD/CAM system. CAD (computer aided design) is a system that obtains the three-dimensional shape of an affected part through 3D scanning and digitizes it. Furthermore, CAM (computeraided design, computer-aided manufacturing) is a system that performs cutting processing on a workpiece based on numerical data generated by CAD, and cuts out a metal frame whose shape is suitable for the affected part. Since the dental CAD/CAM system that combines these systems can easily achieve high dimensional accuracy that has to rely on the skills of dental technicians, it is possible to efficiently form a metal frame that is well-adapted to the affected part. From this point of view, it is expected that Further spread (for example, refer to Patent Document 2.).

Workpieces for dental CAD/CAM systems are generally referred to as "blanks". In addition to the characteristics required for metal frames such as aesthetics, biocompatibility, chemical stability, and wear resistance, the billet must also have machinability. Machinability is a property that enables good machining, and by using a material with good machinability, it is possible to more efficiently cut out a metal frame that accurately reproduces the target shape using CAM based on numerical data generated by CAD.

Although the alloy described in Patent Document 1 is suitable for casting, it has a problem of poor machinability. If the machinability of the material is low, desired processing cannot be performed, and deviations between the processed shape and the desired shape will occur. As a result, the time required for secondary processing due to shape correction is increased, which has the disadvantage of low adaptability to the affected part.

[Prior Art Literature]

【Patent Literature】

Patent Document 1: Japanese Patent Application Laid-Open No. 11-1738

Patent Document 2: Japanese Patent Laid-Open No. 2007-215854

Contents of the invention

The object of the present invention is to provide a dental blank to be machined with good machinability, a metal powder for powder metallurgy capable of producing the above-mentioned machined blank, and a dental metal frame for porcelain with good adhesion to ceramic materials. , and dental restorations with high reliability.

The above objects are achieved by the present invention described below.

The dental material to be machined according to the present invention is characterized in that Co is the main component, and Cr is contained in a ratio of not less than 26% by mass and not more than 35% by mass, and is contained by a ratio of not less than 5% by mass and 12% by mass. % or less contains Mo, contains Si in a mass ratio of 0.3% or more and 2.0% or less in mass ratio, and contains N in a mass ratio of 0.09% or more and 0.5% or less. The blank for processing is composed of a sintered body of metal powder.

Thereby, a structure unique to the sintered body can be formed, and therefore, a dental blank to be machined with good machinability can be obtained.

In the dental material to be machined according to the present invention, in the cross section of the material to be machined, if the surface layer is defined as the surface portion from the surface to the depth of 0.3 mm, the position from the surface to the depth of 5 mm is In the case of an inner layer, the N concentration of the inner layer is preferably 50% or more and 200% or less of the N concentration of the surface layer.

As a result, the physical properties of the inner layer portion and the surface layer portion are close, and when cutting a dental material to be machined, changes in machinability during cutting can be suppressed. Therefore, the dimensional accuracy of the cut out metal frame is difficult to decrease. Furthermore, the portion capable of suppressing the mechanical properties of the metal frame differs.

In the dental material to be machined according to the present invention, in the cross section of the material to be machined, if the surface layer is defined as the surface portion from the surface to the depth of 0.3 mm, the position from the surface to the depth of 5 mm is In the case of an inner layer part, the Vickers hardness of the inner layer part is preferably 67% or more and 150% or less of the Vickers hardness of the surface layer part.

Accordingly, the hardness of the inner layer portion and the surface layer portion are close to each other, and it is possible to suppress a change in machinability during cutting when cutting a dental material to be machined. Therefore, the dimensional accuracy of the cut out metal frame is difficult to decrease.

In the dental workpiece material of the present invention, it is preferable that the Vickers hardness of the inner layer part is 200 or more and 480 or less.

Thereby, it is possible to obtain a material capable of producing a metal frame having sufficient deformation resistance against the occlusal force. Furthermore, since the cutting resistance becomes relatively small, it is possible to obtain a metal frame material which has good machinability and can efficiently cut out a desired shape and size.

In the dental workpiece material of the present invention, it is preferable that the ratio of the above-mentioned N content to the above-mentioned Si content is 0.1 to 0.8.

Thus, high mechanical properties and high machinability can be simultaneously achieved. That is, by adding a certain amount of Si, the machinability can be improved. On the other hand, if the added amount of Si is too large, there is a possibility that the mechanical properties of the material will be reduced. Therefore, when N is added at a ratio within the above range, the high machinability obtained by the addition of Si and the effect obtained by the addition of N will not cancel each other out, so that the machinability can be synergistically improved. sex. Furthermore, the solid solution of N can suppress the distortion of the crystal structure due to the solid solution of Si, and therefore, the reduction of mechanical properties can be prevented. In addition, if Si is added, the crystal structure is distorted, and in this state, a large hysteresis tends to occur due to the behavior of thermal expansion and thermal contraction. If large hysteresis occurs due to the behavior of thermal expansion and thermal contraction, the thermal properties of the billet may change over time. On the other hand, by adding N at the above-mentioned ratio, N can penetrate into the crystal structure and form a solid solution, thereby suppressing distortion of the crystal structure. As a result, hysteresis due to behavior of thermal expansion and thermal contraction can be suppressed, and the thermal properties of the billet can be stabilized.

In the dental material to be machined according to the present invention, it is preferable that a part of the Si is contained as silicon oxide, and the ratio of Si contained as the silicon oxide in the Si is 10% by mass. More than % accounts for less than 90% of the mass ratio.

Thus, the effects of high machinability, high mechanical properties of the metal frame, and high adhesion of ceramic materials can be brought about. On the other hand, due to the presence of a certain amount of silicon oxide, the Co contained in the material can be sufficiently suppressed. The content of oxides of transition metal elements such as , Cr, and Mo. As a result, a higher reliability of the dental prosthesis is achieved.

In the dental workpiece material of the present invention, it is preferable that the silicon oxide is segregated at the grain boundaries of the sintered body.

Thereby, enlargement of metal crystals can be more reliably suppressed, and a material from which a metal frame with better mechanical properties can be cut out can be obtained. Furthermore, since the precipitates of silicon oxide segregated at grain boundaries can naturally maintain an appropriate distance from each other, the precipitates of silicon oxide in the billet can be dispersed more uniformly. As a result, a more homogeneous billet can be obtained.

In the dental material to be machined according to the present invention, it is preferable that in the X-ray diffraction pattern obtained by the X-ray diffraction method using CuKα ray, it is determined based on the ICDD card (International Center for Diffraction Data Card) When the height of the highest peak among the peaks of Co is 1, the ratio of the heights of the highest peak among the peaks of Co ₃ Mo determined based on the quasi-diffraction data card is 0.01 to 0.5.

Thereby, it is possible to obtain a raw material that prevents the decrease in hardness of the metal frame and prevents the dental prosthesis from being deformed due to occlusal force, and at the same time suppresses the decrease in tensile strength, endurance and elongation.

In the dental material to be machined according to the present invention, the dental material to be machined preferably has a 0.2% proof strength of 450 MPa or more, an elongation of 2% or more, and a Young's modulus of 150 GPa or more. .

Thereby, a material from which a metal frame with excellent durability can be manufactured can be obtained.

The metal powder for powder metallurgy of the present invention is characterized in that Co is the main component, and Cr is contained in a ratio of not less than 26% by mass and not more than 35% by mass, and a ratio of not less than 5% by mass and not more than 12% by mass Containing Mo, containing Si at a ratio of not less than 0.3% by mass and not more than 2.0% by mass, and containing N at a ratio of not less than 0.09% by mass and not more than 0.5% by mass, the metal powder for powder metallurgy is used to manufacture dental The billet used for machining.

Thereby, a metal powder for powder metallurgy capable of producing a material to be machined for dental use having excellent machinability can be obtained.

The metal frame for dental porcelain of the present invention is characterized in that Co is the main component, Cr is contained in a ratio of 26% by mass to 35% by mass, and 5% by mass or more is 12% by mass. Mo is contained in the following proportions, Si is contained in a proportion of 0.3% to 2.0% by mass, and N is contained in a proportion of 0.09% to 0.5% by mass. The metal frame is obtained by cutting a dental blank to be processed which is composed of a sintered body of metal powder.

Thus, a dental metal frame for ceramics excellent in adhesion to ceramic materials can be obtained.

The dental prosthesis of the present invention is characterized by comprising: the dental metal frame for ceramics of the present invention; and a ceramic material layer provided on the surface of the dental metal frame for ceramics.

Thus, a highly reliable dental prosthesis in which the dental metal frame for porcelain-for-porcelain and the ceramic material layer are strongly adhered to can be obtained.

In the dental prosthesis of the present invention, it is preferable that the ceramic material layer contains alumina, and the dental prosthesis further has a mollusk between the dental ceramic metal frame and the ceramic material layer. Stone phase.

Thereby, the ceramic material layer and the metal frame are firmly adhered to each other through the mullite phase, and a highly reliable dental prosthesis in which the ceramic material layer is difficult to peel off can be obtained. Moreover, by forming the mullite phase, the wettability of the ceramic material to the metal frame can be improved during the porcelain firing process. Therefore, from this point of view, the adhesion of the ceramic material layer is also improved.

Description of drawings

FIG. 1 is a perspective view showing an embodiment of a dental workpiece blank of the present invention.

Fig. 2 is a longitudinal sectional view of the dental workpiece material shown in Fig. 1 .

Fig. 3 is an example of a Si composition image obtained by the electron beam analyzer of the dental workpiece blank of the present invention.

Fig. 4(a) is an example of an observation image of a dental blank to be processed according to the present invention, and Fig. 4(b) is an example of an observation image of a conventional dental blank to be processed .

Fig. 5 is a diagram for explaining a method of measuring the cutting resistance of the dental material to be machined according to the present invention.

(a) and (b) of FIG. 6 are diagrams showing the trajectory of the machining tool scanning the blank when measuring the cutting resistance of the dental workpiece to be machined according to the present invention.

Fig. 7 is a perspective view showing a state after cutting out an embodiment of the dental porcelain metal frame of the present invention from the base material shown in Fig. 1 .

Fig. 8 is a sectional view taken along line A-A of Fig. 7 .

Fig. 9 is a longitudinal sectional view showing an embodiment of the metal frame for dental porcelain of the present invention.

Fig. 10 is a longitudinal sectional view showing an embodiment of the dental prosthesis of the present invention.

11 is a graph showing the correlation between the N concentration in the dental workpiece material of Sample No. 30 to No. 36 and the Vickers hardness of the surface layer part and the inner layer part.

Detailed ways

Next, the dental blank to be machined, the metal powder for powder metallurgy, the metal frame for dental porcelain, and the dental prosthesis of the present invention will be described in detail based on preferred embodiments shown in the attached drawings.

[Bills for Dental Machining]

First, an embodiment of the dental workpiece blank of the present invention will be described.

FIG. 1 is a perspective view showing an embodiment of a dental blank to be machined according to the present invention, and FIG. 2 is a longitudinal sectional view of the dental blank to be machined shown in FIG. 1 .

A dental blank 1 to be machined (hereinafter referred to simply as "blank 1") shown in FIG. 1 is a member for cutting out a dental metal fitting of a desired shape by subjecting it to cutting. As described above, the dental workpiece to be machined is used in a dental CAD/CAM system and includes "CAD/CAM blanks" and "dental mill blanks" processed by CAM. The dental metal fittings are not particularly limited as long as they can be temporarily or semi-permanently placed in the oral cavity, but the following description is for the case of cutting out the metal frame.

The blank 1 shown in FIG. 1 and FIG. 2 is formed in a disk shape, that is, a cylinder with a height smaller than a diameter, and its upper surface 11 and lower surface 12 form flat surfaces parallel to each other. The shape of the dental workpiece to be machined according to the present invention is not limited to such a disc shape, but may be any shape. For example, shapes such as a rectangular parallelepiped, a cube, a sphere, and a polygonal column may also be used.

The blank 1 shown in FIGS. 1 and 2 is formed in a disk shape, that is, a cylinder with a height smaller than a diameter, and its upper surface 11 and lower surface 12 form flat surfaces parallel to each other. The shape of the dental workpiece to be machined according to the present invention is not limited to such a disc shape, but may be any shape. For example, shapes such as a rectangular parallelepiped, a cube, a sphere, and a polygonal column may also be used.

Such a material 1 is made of a Co-Cr-Mo-Si-N alloy.

Specifically, the alloy constituting the billet 1 is a main component of Co, containing Cr in a ratio of not less than 26% by mass and not more than 35% by mass, and containing Cr in a ratio of not less than 5% by mass and not more than 12% by mass. Mo, an alloy containing Si in a ratio of not less than 0.3% by mass and not more than 2.0% by mass, and containing N in a ratio of not less than 0.09% by mass and not more than 0.5% by mass.

The billet 1 made of this alloy has biocompatibility, chemical stability, and good machinability. Therefore, when cutting the blank 1 to cut out the metal frame, the cutting chips are smoothly discharged, and the roughness of the cut surface is sufficiently small, so that the cutting can be continuously performed for a long time. Furthermore, chipping and wear of the cutting tool can also be suppressed to a minimum. As a result, the cutting amount of the cutting process can reach the expected, so that the cut out metal frame can reach the designed size and shape.

In addition, this metal frame can be attached to the affected area with less discomfort, and can minimize the burden on the patient, while achieving high adhesion and high aesthetics during porcelain firing.

Here, among the elements constituting the alloy, Co (cobalt) is a main component of the alloy constituting the material 1 and greatly affects the basic properties of the material 1 .

The content of Co is set to be the highest among the elements constituting the alloy. Specifically, it is preferably 50% by mass or more and 67.5% by mass or less, more preferably 55% by mass or more and 67% by mass or less. .

Cr (chromium) mainly functions to improve the corrosion resistance of the billet 1 . This is considered to be because the addition of Cr facilitates the formation of a passivation film (Cr ₂ O _{3 ,} etc.) in the alloy and enhances the chemical stability. Improvement in corrosion resistance can be expected to prevent metal ions from being eluted, for example, even when it comes into contact with body fluids. Therefore, the material 1 made of the alloy containing Cr can be said to be a material from which a metal frame with better adaptability to the body can be cut out. Furthermore, by using Cr together with Co, Mo, and Si, the mechanical properties of the metal frame can be improved.

The content of Cr in the alloy constituting the billet 1 is set to be 26% by mass or more and 35% by mass or less. If the content rate of Cr is less than the above-mentioned lower limit, the corrosion resistance of the metal frame cut out from the material 1 will fall. Therefore, there is a concern that elution of metal ions occurs when the metal frame is in contact with body fluids for a long period of time. On the other hand, if the content of Cr is higher than the above-mentioned upper limit, the amount of Cr relative to Mo and Si may be relatively large, and machinability may be reduced. In addition, Co, Mo, and Si are out of balance, and mechanical properties are degraded.

In addition, the Cr content is preferably not less than 27% by mass and not more than 34% by mass, more preferably not less than 28% by mass and not more than 33% by mass.

Mo (molybdenum) mainly functions to improve the corrosion resistance of the billet 1 . That is, adding Mo improves corrosion resistance more than adding Cr. This is because the addition of Mo makes the passivation film mainly made of Cr oxide denser. Therefore, alloys to which Mo is added make it difficult for metal ions to elute, which contributes to the realization of a metal frame with particularly high biocompatibility.

The content of Mo in the alloy constituting the material 1 is not less than 5% by mass and not more than 12% by mass. If the content rate of Mo is less than the above-mentioned lower limit, there is a concern that the corrosion resistance of the metal frame cut out from the material 1 may be insufficient. On the other hand, if the content of Mo is higher than the above-mentioned upper limit, the amount of Mo relative to Cr and Si may be relatively large, and the machinability may decrease.

In addition, the content of Mo is preferably not less than 5.5% by mass and not more than 11% by mass, more preferably not less than 6% by mass and not more than 9% by mass.

In addition, Si (silicon) mainly functions to improve the machinability of the material 1 . By adding Si, silicon oxide obtained by partially oxidizing silicon is generated in the raw material 1 . As silicon oxide, SiO, _SiO2 , etc. are mentioned. When such silicon oxide is generated in the material 1, the metal crystals will be split at this site. Therefore, it is considered that the structure of the material 1 becomes partially discontinuous around silicon oxide. When the billet 1 in this state is cut using a cutting tool, when chips generated from the tip of the cutting tool leave the body of the billet 1, silicon oxide is considered to be a base point and is likely to be separated. As a result, the cutting resistance is reduced, and the machinability of the material 1 is considered to be improved.

On the other hand, Si also plays a role in improving the mechanical properties of the metal frame cut out from the billet 1 . The above-mentioned silicon oxide suppresses the metal crystals from being significantly enlarged when the metal crystals grow in the process of manufacturing the billet 1 . Therefore, in the Si-added alloy, the grain size of the metal crystals can be suppressed to be small, and the mechanical properties of the metal frame can be further improved.

Therefore, by adding Si, both the machinability of the raw material 1 and the mechanical properties of the metal frame cut out from the raw material 1 can be realized.

Furthermore, by adding Si, the adhesion of the ceramic material to the metal frame cut out from the blank 1 can be improved. Therefore, when the ceramic material layer is provided so as to cover the surface of the metal frame, peeling of the ceramic material layer can be suppressed, and a highly reliable dental prosthesis can be obtained.

Furthermore, in order to obtain the above effects, the content of Si needs to be set to 0.3% by mass or more and 2.0% by mass or less. If the content of Si is lower than the above-mentioned lower limit, the amount of silicon oxide will decrease, so the cutting resistance will increase, the machinability of the blank 1 will decrease, and at the same time, the metal crystals will easily become enlarged when the blank 1 is produced, Therefore, there is a high possibility that the mechanical properties of the metal frame cut out from the blank 1 will be degraded. Furthermore, since the adhesiveness of the ceramic material to the metal frame becomes insufficient, defects such as peeling of the ceramic material layer tend to occur in the dental prosthesis. On the other hand, if the content of Si exceeds the above-mentioned upper limit, too much silicon oxide will be present in the material 1, and regions where silicon oxide is spatially continuously distributed tend to occur. Since the structure of the blank 1 is discontinuous to a certain extent in this region, this region tends to become a starting point of damage when an external force is applied to the blank 1 . Therefore, the mechanical properties of the billet 1 are lowered.

In addition, the content of Si is preferably not less than 0.5% by mass and not more than 1.0% by mass, more preferably not less than 0.6% by mass and not more than 0.9% by mass.

In addition, it is preferable that a part of Si exists in the state of silicon oxide as described above, but in the amount of Si, the ratio of Si contained as silicon oxide is preferably 10% by mass or more with respect to the total amount of Si. The ratio is less than 90%, more preferably more than 20% by mass and less than 80% by mass, more preferably more than 30% by mass and less than 70% by mass, especially preferably more than 35% by mass and 65% by mass %the following. By setting the ratio of Si contained as silicon oxide in the total Si within the above range, the raw material 1 can achieve the above-mentioned machinability, mechanical properties of the metal frame, and adhesion to ceramic materials. On the one hand, due to the presence of a certain amount of silicon oxide, the amount of oxides of transition metal elements such as Co, Cr, and Mo contained in the material 1 can be sufficiently suppressed. That is to say, since Si is easier to oxidize than Co, Cr, and Mo, Si takes away the oxygen combined with these transition metal elements to cause a reduction reaction. Therefore, considering that the total amount of Si is not silicon oxide, it is equivalent to making the transition Metal elements undergo a sufficient reduction reaction. Therefore, by setting the ratio of Si contained as silicon oxide in Si within the above-mentioned range, the above-mentioned effects of high machinability, high mechanical properties of the metal frame, and high adhesion of ceramic materials in the material 1 can be suppressed. Hindered by Co, Cr or Mo oxides. As a result, a more reliable dental prosthesis can be realized.

Furthermore, by setting the ratio of Si contained as silicon oxide in Si within the above-mentioned range, it is possible to impart appropriate hardness to the material 1 . That is, due to the presence of a certain amount of Si other than silicon oxide, at least one of Co, Cr, and Mo forms a hard intermetallic compound with Si, which can increase the hardness of the billet 1 . Since the hardness of the blank 1 is increased, the hardness of the metal frame cut out from the blank 1 is also correspondingly increased. Therefore, after the dental prosthesis including the metal frame is installed on the affected part, it is difficult to damage it due to the occlusal force. deformed, it will become a highly reliable dental prosthesis. In other words, since the addition of Si inhibits the significant growth of metal crystals, the hardness of the material 1 tends to decrease from this point of view, but since a part of Si forms intermetallic compounds, this significant decrease in hardness can be suppressed, thereby Reliability as a dental prosthesis can be ensured.

Such an intermetallic compound is not particularly limited, and examples include CoSi ₂ , Cr ₃ Si, MoSi ₂ , Mo ₅ Si ₃ and the like.

In addition, the ratio of Si contained as silicon oxide to the total amount of Si can be obtained by a gravimetric method and an ICP emission spectrometry.

Furthermore, considering the precipitation amount of intermetallic compounds, the ratio of the Si content (Si/Mo) to the Mo content is preferably a mass ratio of 0.05 to 0.2, and more preferably 0.08 to 0.15. Accordingly, it is possible to obtain a blank 1 capable of producing a highly reliable dental prosthesis while suppressing a significant decrease in the machinability of the blank 1 .

Furthermore, silicon oxide may be distributed anywhere, but is preferably distributed so as to be segregated at grain boundaries (interfaces between metal crystals). By segregating silicon oxide in such a position, it is possible to obtain a raw material 1 that can more reliably suppress the enlargement of metal crystals and cut out a metal frame with better mechanical properties. In addition, since the precipitates of silicon oxide segregated at the grain boundaries naturally keep an appropriate distance from each other, the precipitates of silicon oxide in the material 1 can be dispersed more uniformly. As a result, a more homogeneous material 1 can be obtained.

Such a blank material 1 is advantageous in minimizing individual differences in properties between metal frames even when a plurality of metal frames are cut out therefrom.

Furthermore, the size, distribution, etc. of segregated silicon oxide precipitates can be identified by surface analysis in qualitative analysis. Specifically, in the Si composition image obtained using an electron beam analyzer (EPMA), the average diameter of Si in the segregation region is preferably 0.1 μm to 10 μm, more preferably 0.3 μm to 8 μm. If the average diameter of Si in the segregation region is within the above-mentioned range, the size of the precipitates of silicon oxide is optimal in achieving the above-mentioned various effects. That is, if the average diameter of Si in the segregation region is lower than the above-mentioned lower limit value, the precipitates of silicon oxide will not segregate in a sufficient size, and the above-mentioned various effects may not be sufficiently achieved. On the other hand, if Si is in the segregation region If the average diameter exceeds the above-mentioned upper limit, the mechanical properties of the billet 1 may decrease.

In addition, in the Si composition image, the average diameter of Si in the segregated region can be obtained as an average value of the diameters of circles having the same area as the area of the Si segregated region (projected area equivalent circle diameter). In addition, the average diameter of Si in segregated regions is obtained by measuring the average value of 100 or more regions in which Si is segregated.

Fig. 3 is an example of a Si composition image obtained by the electron beam analyzer of the dental workpiece blank of the present invention.

As can be seen from this compositional image, in the dental material to be machined according to the present invention, Si is locally aggregated and the aggregates (light-colored portion in FIG. 3 ) are dispersed. Consider this to indicate the segregation of silicon oxide at grain boundaries.

Furthermore, the material 1 includes a first phase (phase) mainly composed of Co and a second phase mainly composed of Co ₃ Mo. Among them, by containing the second phase, it is possible to impart appropriate hardness to the metal frame similarly to the above-mentioned intermetallic compound containing Si, so that a useful material 1 can be obtained from the viewpoint of improving the reliability of the dental prosthesis. On the other hand, if the second phase is contained in excess, mechanical properties such as tensile strength, strength, and elongation may decrease because it is likely to segregate.

Therefore, from the above viewpoint, it is preferable to contain the first phase and the second phase at an appropriate ratio. Specifically, when the crystal structure of material 1 was analyzed by X-ray diffraction using CuKα rays, and the height of the highest peak among the peaks due to Co was set to 1, the highest peak among the peaks due to _Co3Mo The height of is preferably not less than 0.01 and not more than 0.5, and more preferably not less than 0.02 and not more than 0.4.

Moreover, if the ratio of the above-mentioned peak height of Co ₃ Mo when the above-mentioned peak height of Co is 1 is lower than the above-mentioned lower limit value, the ratio of Co ₃ Mo to Co in the material 1 will decrease, so the hardness of the metal frame will be reduced. will be lowered, worrying about making the dental prosthesis susceptible to deformation due to occlusal forces. On the other hand, if the ratio of the above-mentioned peak heights of Co ₃ Mo exceeds the above-mentioned upper limit, Co ₃ Mo will be present in excess, and therefore Co ₃ Mo will be likely to segregate, which may lower the tensile strength and resistance, and cause the tensile strength to decrease. Length also decreased.

In addition, CuKα rays are generally characteristic X-rays with an energy of 8.048keV.

In addition, when specifying the peak derived from Co, it is necessary to specify based on the Co database of the ICDD (The International Center for Diffraction Data, International Center for Diffraction Data) card. Similarly, when determining the peak originating from Co ₃ Mo, it is necessary to determine based on the Co ₃ Mo database of the ICDD card.

Furthermore, in the raw material 1, the abundance ratio of Co ₃ Mo is preferably not less than 0.01% by mass and not more than 10% by mass, more preferably not less than 0.05% by mass and not more than 5% by mass. As a result, a metal frame having appropriate hardness, tensile strength, durability, and elongation can be obtained, thereby obtaining a dental prosthesis that is hardly deformed by occlusal force.

In addition, these abundance ratios can be obtained by quantifying the abundance ratio of Co ₃ Mo from the results of crystal structure analysis.

Also, the main role of N (nitrogen) is to improve the mechanical properties of the billet 1 . Since N is an austenitizing element, it promotes the austenitization of the crystal structure of the material 1 and suppresses an increase in the hardness of the material 1, and also plays a role of improving toughness.

Furthermore, by containing N, in the material 1 made of a sintered body of metal powder, the formation of a dendrite phase is suppressed, and the content of the dendrite phase becomes very small. From such a point of view, the increase in hardness of the material 1 can be suppressed, and the toughness can also be improved.

Furthermore, as described above, the material 1 containing N has appropriate hardness and high toughness, and is a material with a low dendrite phase content. Therefore, such a material 1 has high machinability and can efficiently cut out a metal frame with high dimensional accuracy.

Here, the dendrite phase is a crystal structure that grows into a dendrite, and the material 1 containing a large amount of such a dendrite phase will have lower machinability. Therefore, reducing the content of the dendrite phase is effective in improving the machinability of the material 1 . Specifically, the area ratio of the dendrite phase in the observation image obtained by observing the material 1 using a scanning electron microscope is preferably 20% or less, more preferably 10% or less. The material 1 satisfying these conditions is particularly excellent in mechanical properties and machinability.

Furthermore, as described above, the blank 1 is composed of a sintered body of metal powder. The volume of each particle of the metal powder is very small, the cooling rate is high, and the uniformity of cooling is also high. Therefore, in the green material 1 composed of such a sintered body of metal powder, the generation of dendrite phase is suppressed. On the other hand, with conventional methods such as casting, the volume to be cooled is very large because molten metal is poured into a mold that forms the shape of the billet. Therefore, the cooling rate is low, and the uniformity of cooling is also low. As a result, a large number of dendrite phases are formed in billets produced by this method.

In addition, the above-mentioned area ratio is calculated as a ratio of the area occupied by the dendrite phase to the area of the observation image, and one side of the observation image is set to be approximately 50 μm or more and 1000 μm or less.

In order to obtain the above-mentioned effects, the content of N needs to be set to not less than 0.09% by mass and not more than 0.5% by mass. If the N content is lower than the above lower limit, the crystal structure of the material 1 will not be sufficiently austenitized, so the hardness of the material 1 will be very high, and the toughness will also decrease. Therefore, the machinability and mechanical properties of the raw material 1 are lowered. This is considered to be due to the precipitation of a large amount of hexagonal close-packed (hcp) structure (ε phase) in addition to the austenite phase (γ phase) in the material 1 . On the other hand, if the content of N is higher than the above-mentioned upper limit, a large amount of various nitrides will be formed, and the composition will be difficult to sinter. Therefore, the sintered density of the green material 1 is lowered, and the mechanical properties are also lowered. Examples of nitrides to be formed include Cr ₂ N and the like. If such nitrides are precipitated, the hardness will increase, but the toughness will still decrease.

In addition, the content of N is preferably not less than 0.12% by mass and not more than 0.4% by mass, more preferably not less than 0.14% by mass and not more than 0.25% by mass, especially preferably not less than 0.15% by mass and not more than 0.22% by mass. %the following.

Especially in the range of more than 0.15% by mass and less than 0.22% by mass, it can be observed that the austenite phase is particularly dominant, the hardness is significantly reduced, and the toughness is obviously improved. When the billet 1 at this time was subjected to crystal structure analysis by X-ray diffraction method using CrKα ray, it was observed that the main peak originating from the austenite phase was very strong, and on the other hand, the main peak originating from the hexagonal close-packed structure was observed. Both peaks and other peaks are less than 5% of the height of the main peak. It can be seen that the austenite phase is dominant.

On the other hand, the ratio of the N content to the Si content (N/Si) is preferably a mass ratio of 0.1 to 0.8, more preferably 0.2 to 0.6. Accordingly, both high mechanical properties and high machinability can be achieved. That is, by adding a certain amount of Si, the machinability is enhanced as described above. On the other hand, if the amount of Si added is too large, there is a concern that the mechanical properties of the material 1 may be reduced. Therefore, if N is added at a ratio within the above range, the high machinability obtained by the addition of Si and the above effect obtained by the addition of N will work without canceling each other out, so synergistic improvement can be achieved. machinability. This is considered because metal elements such as Si and Co form substitution-type solid solutions, and metal elements such as N and Co form intrusion-type solid solutions, so that they can coexist with each other. Furthermore, the distortion of the crystal structure caused by the solid solution of Si is suppressed by the solid solution of N. Therefore, reduction in mechanical characteristics can be prevented.

Furthermore, if Si is added, the crystal structure is distorted as described above, and a large hysteresis tends to occur due to the behavior of thermal expansion and thermal contraction in this state. If there is a large hysteresis due to the behavior of thermal expansion and thermal contraction, there is a concern that the thermal properties of the billet 1 will change over time.

In contrast, by adding N in the above ratio, distortion of the crystal structure is suppressed due to N intrusion into the crystal structure. As a result, hysteresis due to behavior of thermal expansion and thermal contraction can be suppressed, so that the thermal characteristics of the billet 1 can be stabilized.

From the above, by appropriately adding Si and N, the machinability of the material 1 can be improved, and the stability of the mechanical properties and the stability of the thermal properties can be achieved, respectively.

In addition, if the ratio of the N content to the Si content is below the above lower limit, the distortion of the crystal structure cannot be sufficiently suppressed, and there is a concern that the toughness and the like may decrease. On the other hand, if it exceeds the above-mentioned upper limit, there is a possibility that a composition that is difficult to sinter will be formed, the sintered density of the green material 1 will decrease, and the mechanical properties will also decrease.

In addition, the alloy constituting the material 1 may contain C (carbon) in addition to the above elements. By adding C, the hardness and tensile strength of the billet 1 can be enhanced, and machinability can also be enhanced. The detailed reason for the enhanced machinability is not clear, but the reduction of cutting resistance due to the formation of carbides is one of the reasons. Furthermore, since C forms an intrusive solid solution with metal elements such as Co, even if C is added, the decrease in toughness (increase in brittleness) hardly occurs. Therefore, machinability can be improved while maintaining a certain toughness.

The content of C in the alloy constituting the material 1 is not particularly limited, but is preferably 1.5% by mass or less, more preferably 0.7% by mass or less. When the content of C exceeds the above-mentioned upper limit, the brittleness of the material 1 may increase and the mechanical properties may also decrease.

In addition, the lower limit of the added amount is not particularly limited, but it is preferable to set the lower limit to about 0.05% by mass in order to fully exhibit the above effects.

Furthermore, the C content is preferably about 0.02 to 0.5 times the Si content, more preferably about 0.05 to 0.3 times. By setting the ratio of C to Si within the above range, the adverse effects of silicon oxide and carbide on the mechanical properties of the material 1 can be minimized, and at the same time, a synergistic effect can be exerted on the improvement of machinability. Therefore, a material 1 having particularly excellent machinability can be obtained.

Furthermore, the content of N is preferably about 0.3 to 10 times the content of C, more preferably about 2 to 8 times. By setting the ratio of N to C within the above range, the machinability of the raw material 1 enhanced by the addition of C and the mechanical properties of the raw material 1 improved by the addition of N can be realized at the same time.

In addition, in the alloy constituting the material 1, in addition to the above-mentioned various elements, it is allowed to add a small amount of additives intentionally within the range that does not hinder the above-mentioned effects, and it is also allowed to mix unavoidable impurities during production. In this case, the total content of additives and impurities is preferably 1% by mass or less, more preferably 0.5% by mass or less, even more preferably 0.2% by mass or less. Examples of such additive elements and impurity elements include Li, B, N, O, Na, Mg, Al, P, S, Mn, K, Ca, Sc, Ti, V, Co, Zn, Ga, Ge , Y, Pd, Ag, In, Sn, Sb, Hf, Ta, W, Os, Ir, Pt, Au, Bi, etc.

On the other hand, the alloy constituting the material 1 preferably does not substantially contain Ni (nickel). Conventional billets often contain a certain amount of Ni in order to ensure plastic workability, but Ni is sometimes treated as a metal allergy-inducing substance, and it is also an element that is concerned that it may affect living organisms. In the alloy constituting the billet 1 , Ni is not added as a constituent element other than Ni which is unavoidably mixed during manufacture. Therefore, the metal frame cut out from the material 1 according to the present invention is less prone to metal allergy, and has particularly high biocompatibility. In addition, in the present invention, since an appropriate amount of Si is added, the material 1 having sufficient machinability can be realized even without adding Ni. Furthermore, in consideration of unavoidable contamination, the Ni content is preferably 0.05% by mass or less, more preferably 0.03% by mass or less.

Furthermore, in the alloy constituting the billet 1, the balance of the above-mentioned elements is Co. As described above, the content of Co is set to be the highest among the elements contained in the alloy constituting the material 1 .

In addition, each constituent element and the composition ratio of the alloy constituting the material 1 can be emitted by, for example, iron and steel-atomic absorption method specified in JIS G1257 (2000) and iron and steel-ICP specified in JIS G 1258 (2007). Analytical method, iron and steel specified in JIS G1253 (2002) - spark emission analysis method, iron and steel specified in JIS G 1256 (1997) - X-ray fluorescence analysis method, gravimetric method specified in JIS G 1211 to G 1237 Titration, absorptiometry, etc. to specify. Specifically, for example: solid-state luminescence spectroscopic analyzer (spark luminescence analyzer) manufactured by SPECTRO, model: SPECTROLAB, type: LAVMBO8A.

In addition, JIS G 1211 to G 1237 are as follows.

JIS G 1211(2011) Iron and Steel-Carbon Quantitative Method

JIS G 1212(1997) Iron and Steel-Silicon Quantitative Method

JIS G 1213(2001) Quantitative method of manganese in iron and steel

JIS G 1214(1998) Iron and Steel - Quantitative Method of Phosphorus

JIS G 1215(2010) Iron and Steel-Sulfur Quantitative Method

JIS G 1216(1997) Iron and Steel - Nickel Quantitative Method

JIS G 1217(2005) Iron and Steel - Chromium Quantitative Method

JIS G 1218(1999) Iron and Steel - Molybdenum Quantitative Method

JIS G 1219(1997) Iron and steel-copper quantitative method

JIS G 1220(1994) Iron and Steel - Tungsten Quantitative Method

JIS G 1221(1998) Iron and Steel - Quantitative Method of Vanadium

JIS G 1222(1999) Iron and Steel - Cobalt Quantitative Method

JIS G 1223(1997) Quantitative method for iron and steel-titanium

JIS G 1224(2001) Quantitative method of aluminum in iron and steel

JIS G 1225(2006) Iron and Steel - Quantitative Method for Arsenic

JIS G 1226(1994) Iron and Steel - Tin Quantitative Method

JIS G 1227(1999) Quantitative method of boron in iron and steel

JIS G 1228(2006) Iron and Steel - Nitrogen Quantitative Method

JIS G 1229(1994) Steel-lead quantitative method

JIS G 1232(1980) Quantitative method for zirconium in steel

JIS G 1233(1994) Steel-selenium quantitative method

JIS G 1234(1981) Quantitative method for tellurium in steel

JIS G 1235(1981) Quantitative method of antimony in iron and steel

JIS G 1236(1992) Quantitative method of tantalum in steel

JIS G 1237(1997) Iron and Steel - Niobium Quantitative Method

Furthermore, when specifying C (carbon) and S (sulfur), the oxygen flow combustion (combustion in a high-frequency induction heating furnace)-infrared ray absorption method stipulated in JIS G 1211 (2011) can also be used. Specifically, for example, CS-200 carbon-sulfur analyzer manufactured by LECO Corporation.

In addition, when specifying N (nitrogen) and O (oxygen), the nitrogen quantitative method for iron and steel specified in JIS G 1228 (2006) and the oxygen content of metal materials specified in JIS Z 2613 (2006) can also be used. quantitative method. Specifically, for example, an oxygen/nitrogen analyzer manufactured by LECO Corporation, TC-300/EF-300.

Furthermore, the blank 1 shown in FIG. 1 is composed of a sintered body of metal powder, that is, manufactured by powder metallurgy. Such a billet 1 has superior mechanical properties such as hardness, tensile strength, endurance, elongation, etc., compared with, for example, a billet (cast material) produced by a casting method. This is because the billet 1 produced by the powder metallurgy method is manufactured using rapidly cooled metal powder (small in size, easy to rapidly cooled), and it is difficult to produce significant grain growth of metal crystals compared with casting methods, etc. Therefore, The consideration is based on the unique characteristic of sintered body that it is difficult to generate hypertrophic metal crystals. Furthermore, since the powder metallurgy method is used, the composition is easily homogeneous, and therefore the distribution of Si and silicon oxide is also easy to be uniform. Therefore, the raw material 1 which is also uniform in machinability can be obtained.

As the metal powder (the metal powder for powder metallurgy of the present invention) used in the production of the billet 1 , the powder composed of the alloy described above can be used. The average particle diameter is preferably 3 μm to 100 μm, more preferably 4 μm to 80 μm, and still more preferably 5 μm to 60 μm. By using a metal powder having such a particle size, a billet 1 having a high density, high mechanical properties, and excellent machinability can be produced.

In addition, in the particle size distribution obtained by the laser diffraction method, the average particle diameter is calculated as the particle diameter when the cumulative amount from the diameter side is 50% calculated on a mass basis.

Furthermore, when the average particle size of the metal powder is less than the above-mentioned lower limit, the formability of powder metallurgy decreases, so the density of the material 1 may decrease, and the mechanical properties of the metal frame may decrease. On the other hand, when the average particle size of the metal powder exceeds the above upper limit, since the filling property of the metal powder in powder metallurgy is lowered, there is a concern that the density of the blank 1 will be lowered and the mechanical properties of the metal frame will be lowered. . Furthermore, there is a concern that the uniformity of the composition may be impaired, and the machinability of the billet 1 may be reduced.

Also, the particle size distribution of the metal powder is preferably as narrow as possible. Specifically, if the average particle diameter of the metal powder is within the above range, the maximum particle diameter is preferably 200 μm or less, more preferably 150 μm or less. By controlling the maximum particle size of the metal powder within the above range, the particle size distribution of the metal powder can be made narrower, so that the mechanical properties and machinability of the blank 1 can be further improved.

In addition, the above-mentioned maximum particle diameter refers to the particle diameter at which the cumulative amount from the diameter side reaches 99.9% by mass standard calculation in the particle size distribution obtained by the laser diffraction method.

Furthermore, when the short axis of the metal powder particles is PS [μm] and the long axis is PL [μm], the average value of the aspect ratio defined by PS/PL is preferably from 0.4 to 1, more preferably from 0.7 to 1 the following degree. Metal powders with such an aspect ratio can increase the filling rate during powder compaction because their shapes are closer to spherical. As a result, a material 1 having high mechanical properties and machinability can be obtained.

In addition, the above-mentioned major axis means the maximum length obtained in the projected image of the particles, and the above-mentioned short axis means the maximum length in the direction perpendicular to the maximum length. In addition, the average value of aspect ratio was calculated|required as the average value of the measured value of 100 or more metal powder particles.

On the other hand, in the cross section of the material 1, when the major axis of the crystal structure is CL and the minor axis is CS, the average value of the aspect ratio defined by CS/CL is preferably about 0.4 to 1, more preferably 0.5 or more and 1 or less. Since the anisotropy of the crystalline structure of such an aspect ratio is small, it contributes to the realization of the raw material 1 of a metal frame that can exhibit good mechanical properties such as endurance regardless of the direction of force application. That is, the metal frame cut out from such a blank 1 has good fracture resistance no matter what posture it is used in, so it is useful without limiting its use position in the oral cavity. In other words, using such a material 1 , it is possible to manufacture a metal frame that exhibits good mechanical properties regardless of the cutting method of the metal frame.

In addition, the above-mentioned major axis is the maximum length that can be obtained by one crystal structure in the observed image of the cross section of the billet 1, and the above-mentioned short axis is the maximum length in the direction perpendicular to the maximum length. In addition, the average value of the aspect ratio is calculated|required as the average value of the measured value of 100 or more crystal structures.

Furthermore, it is preferable that the blank 1 has fine independent pores inside it. By having such voids, the material 1 becomes a material particularly excellent in machinability. This is because the existence of independent voids can suppress the degradation of the mechanical properties of the blank 1. At the same time, the voids serve as the starting point, making it easier for chips generated during cutting to leave the body of the blank 1, thereby achieving cutting resistance. greatly reduced effect.

Furthermore, by making the blank 1 have voids, the metal frame cut out from the blank 1 also has voids that are open on the surface. When ceramicing the metal frame, the constituent material of the pottery can be made to enter the voids. Therefore, it contributes to improving the adhesion between the metal frame and the ceramic material. As a result, when the ceramic layer is provided to cover the surface of the metal frame, peeling of the ceramic layer can be suppressed and a highly reliable dental prosthesis can be obtained.

The average diameter of the pores is preferably not less than 0.1 μm and not more than 10 μm, more preferably not less than 0.3 μm and not more than 8 μm. If the average diameter of the pores is within the above range, the material 1 having higher machinability can be obtained. That is, if the average diameter of the pores is less than the above lower limit, the machinability may not be sufficiently improved. On the other hand, if the average diameter of the pores exceeds the above upper limit, the mechanical properties of the material 1 may be reduced.

In addition, in the scanning electron microscope image, the average diameter of the pores can be obtained as an average value of the diameters of circles having the same area as the area of the pores (circle-equivalent diameter of the projected area). In addition, the average diameter of pores can be obtained as an average value of measured values of 100 or more pores.

Furthermore, in the observed image of the material 1 , the area ratio occupied by voids is preferably from 0.001% to 1%, more preferably from 0.005% to 0.5%. If the area ratio of the pores is within the above range, the material 1 can have more excellent mechanical properties and machinability at the same time.

In addition, the area ratio is calculated as the area ratio of the voids to the area of the observation image, and one side of the observation image can be set to approximately 50 μm or more and 1000 μm or less.

Fig. 4(a) is an example of an observation image of a dental blank to be processed according to the present invention, and Fig. 4(b) is an example of an observation image of a conventional dental blank to be processed .

In the observation image shown in (a) of FIG. 4 , the presence of substantially uniformly dispersed voids can be observed. On the other hand, in the observation image shown in (b) of FIG. 4 , a dendritic structure (dendritic phase ).

Furthermore, the Vickers hardness of the material 1 is preferably not less than 200 and not more than 480, more preferably not less than 240 and not more than 380. A blank material 1 of this hardness can produce a metal frame having sufficient deformation resistance even against a occlusal force. Furthermore, the material 1 with such hardness has relatively low cutting resistance, and therefore has excellent machinability, and it will become a material from which a metal frame of a desired shape and size can be effectively cut out.

In addition, the Vickers hardness of the material 1 was measured according to the test method prescribed|regulated by JIS Z 2244 (2009).

Furthermore, the tensile strength of the material 1 is preferably 520 MPa or more, more preferably 600 MPa or more and 1500 MPa or less. The material 1 having such a tensile strength becomes a material from which a metal frame excellent in durability can be produced. Moreover, machinability is also excellent.

Similarly, the 0.2% proof strength of the material 1 is preferably 450 MPa or more, more preferably 500 MPa or more and 1200 MPa or less. Such a 0.2% proof material 1 will be a material from which a metal frame excellent in durability can be manufactured. Moreover, machinability is also excellent.

These tensile strengths and 0.2% proof strength were measured in accordance with the test method specified in JIS Z 2241 (2011).

Furthermore, the elongation of the material 1 is preferably not less than 2% and not more than 50%, more preferably not less than 10% and not more than 45%. Since the material 1 having such an elongation is less prone to chipping and cracking, it becomes a material having excellent machinability.

The elongation (elongation at break) of the material 1 was measured in accordance with the test method specified in JIS Z 2241 (2011).

Furthermore, the Young's modulus of the material 1 is preferably 150 GPa or more, more preferably 170 GPa or more and 300 GPa or less. Since the material 1 having such a Young's modulus becomes difficult to deform, cutting with high dimensional accuracy is possible, and at the same time, a metal frame that is hardly deformed by the occlusal force can be realized. Moreover, machinability is also excellent.

Furthermore, the fatigue strength of the material 1 is preferably 250 MPa or more, more preferably 350 MPa or more, and still more preferably 500 MPa or more and 1000 MPa or less. The material 1 having such a fatigue strength can be used in an environment where fatigue cracks and the like can be suppressed and can exhibit its function for a long period of time even if it is used in an environment where it is in contact with body fluids in the oral cavity, for example. Billet of metal frame.

In addition, the fatigue strength of the material 1 was measured according to the test method prescribed|regulated by JIS T 0309 (2009). Assuming that the applied waveform of the load corresponding to the repeated stress is a sine wave, the stress ratio (minimum stress/maximum stress) is 0.1. Also, assume that the repetition frequency is 30 Hz and the number of repetitions is 1×10 ⁷ times.

Furthermore, as described above, such a material 1 is a material having good machinability due to its low cutting resistance.

That is, the cutting resistance of the billet 1 is smaller than the cutting resistance of the molten material having the same composition as the metal powder used in the manufacture of the billet 1 . The small cutting resistance helps to control the vibration amplitude of the machining tool within a small range during cutting. Therefore, when the blank 1 is cut, a desired shape can be easily and accurately cut out, and therefore a metal frame with high dimensional accuracy can be manufactured.

Specifically, the cutting resistance of the material 1 is preferably 300N or less, more preferably 250N or less, even more preferably 200N or less. The material 1 that can be processed with such a small cutting resistance has high machinability and can be processed with high processing accuracy.

In addition, the cutting resistance of the material 1 can be measured using, for example, a three-component cutting force gauge.

FIG. 5 is a diagram for explaining a method of measuring the cutting resistance of the material 1 .

When measuring the cutting resistance of the material 1 , first, as shown in FIG. 5 , it is necessary to place a three-component cutting force gauge 7 on a stage 74 of the processing device. Next, the blank 1 is fixed to the measuring portion 71 of the three-component cutting force gauge 7 . A jig 72 using screws was used for fixing, and the screw tightening torque was 30 kN. In this state, the blank 1 is cut using the machining tool 73 . Then, the maximum value among the cutting resistances of three-directional components (x component, y component, and z component) measured by the three-component cutting force gauge 7 during machining can be adopted as the cutting resistance of the billet 1 . Furthermore, the cutting resistance in wet machining is the cutting resistance when machining is performed using a cutting fluid.

FIG. 6 is a diagram showing a trajectory TR of the machining tool 73 scanned with respect to the material 1 when measuring the cutting resistance of the material 1 . When measuring the cutting resistance of the material 1 , it is only necessary to scan the machining tool 73 along the trajectory TR of the outer shape of the material 1 . For example, when the outer shape of the blank 1 is circular, as shown in (a) of FIG. In the case of a square, as shown in (b) of FIG. 6 , it is only necessary to scan the processing tool 73 by drawing a quadrangular trajectory TR.

Furthermore, as the metal powder used in the production of the billet 1, metal powder produced by an atomization method (for example, a water atomization method, a gas atomization method, a high-speed rotary water flow atomization method, etc.), Various powdering methods such as reduction method, carbonyl method, pulverization method, etc.

Among them, the material produced by the atomization method is preferably used, and the material produced by the water atomization method or the high-speed rotary water atomization method is more preferably used. The atomization method is a method of producing metal powder by colliding molten metal (melt metal) with a fluid (liquid or gas) sprayed at a high speed, cooling the molten metal while micronizing it. By producing metal powders using this atomization method, extremely fine powders can be produced efficiently. Moreover, the particle shape of the obtained powder is close to spherical due to the effect of surface tension. Therefore, when metal powder is molded by powder metallurgy, a molded body with a high filling rate can be obtained. As a result, a material 1 excellent in mechanical properties can be obtained.

In addition, as the atomization method, in the case of using the water atomization method, the pressure of the water sprayed on the molten metal (hereinafter referred to as "atomized water") is not particularly limited, but is preferably 75 MPa or more and 120 MPa or less (750 kgf /cm ² to 1200 kgf/cm ² ), more preferably 90 MPa to 120 MPa (900 kgf/cm ² to 1200 kgf/cm ² ).

Furthermore, the water temperature of the atomized water is not particularly limited, but is preferably about 1°C to 20°C.

In addition, the atomized water often has an apex on the falling path of the molten metal, and is sprayed in a conical shape such that the outer diameter gradually decreases downward. In this case, the apex angle θ of the cone formed by the atomized water is preferably about 10° to 40°, and more preferably about 15° to 35°. Thereby, the metal powder of the said composition can be manufactured reliably.

Furthermore, the molten metal can be cooled particularly rapidly by means of water atomization, especially high-speed rotary water atomization. Therefore, a homogeneous material 1 having excellent mechanical properties and machinability can be obtained.

Furthermore, the cooling rate when cooling the molten metal using the atomization method is preferably 1×104°C/s or higher, more preferably 1×105°C/s or higher. Through such rapid cooling, metal powder having a particularly small particle size of metal crystals can be obtained.

In addition, when the raw material is melted to obtain molten metal, assuming that the melting point of the constituent material of the billet 1 is Tm, it is preferable to set the melting temperature of the raw material to about Tm+50°C or higher and Tm+300°C lower, more preferably set to It is about Tm+100°C or higher and Tm+200°C or lower. This makes it easy to control and stabilize the generation of alloys when the molten metal is collided with a fluid to be pulverized. That is, while suppressing the enlargement of the crystal structure, it is easy to produce an alloy with high purity (low oxygen content). Therefore, it is possible to produce a metal powder particularly suitable for production of the billet 1 .

The metal powder thus obtained is molded by various molding methods to obtain a molded body. As a molding method, a press molding method, an extrusion molding method, an injection molding method, etc. are mentioned, for example.

Then, by degreasing and firing the obtained molded body, a sintered body (blank 1) can be obtained. The firing temperature can be appropriately set according to the alloy composition, and as an example, it can be set at about 900°C to 1400°C.

Furthermore, the sintered body obtained in this way may be further subjected to HIP treatment (hot isostatic pressing treatment) or the like. As a result, a higher density of the sintered body can be realized, and the green material 1 with better mechanical properties can be obtained.

The conditions for the HIP treatment are, for example, a temperature of 850° C. to 1200° C., and a time of about 1 hour to 10 hours.

Furthermore, the applied pressure is preferably 50 MPa or more, more preferably 100 MPa or more.

In addition, the material 1 is composed of a sintered body obtained by solid-dissolving N in a metal material from the time of powder production, and using the powder. Therefore, in the material 1, N can be distributed substantially uniformly, and physical properties can also be made substantially the same. Therefore, when a plurality of metal frames are cut out from the above-mentioned raw material 1, the properties of the respective metal frames can be made uniform and individual differences can be suppressed.

Specifically, for example, when the thickness of the blank 1 is 10 mm or more, in the section along the thickness direction of the blank 1, the position from the surface to a depth of 0.3 mm is defined as the surface layer, and the position from the surface to a depth of 5 mm is defined as the surface layer portion. inner part.

In this case, the N concentration in the inner layer is preferably 50% to 200% of the N concentration in the surface layer, more preferably 60% to 175%, and even more preferably 75% to 150%. If the concentration of N in the inner layer is below the above-mentioned lower limit or higher than the above-mentioned upper limit, then due to the difference in physical properties between the inner layer and the surface layer, when cutting the billet 1, there is concern about machinability during cutting. will change. Therefore, there is a possibility that the dimensional accuracy of the cut out metal frame will be reduced. Also, the mechanical properties of the metal frame may also be partially different.

In addition, the concentration of N in the inner layer part and the surface layer part can be obtained based on quantitative analysis of N using an electron beam analyzer (EPMA). In this case, the concentration distribution of N in the thickness direction of the material 1 can be obtained by performing line analysis from the surface to the inside of the material 1, and therefore the N concentrations in the inner layer portion and the surface layer portion can be efficiently obtained. .

In addition, in such a material 1 , the Vickers hardness of the inner layer portion is preferably 67% to 150% of the Vickers hardness of the surface layer portion, and more preferably 75% to 125% inclusive. If the concentration of N in the inner layer is lower than the above-mentioned lower limit or higher than the above-mentioned upper limit, the hardness of the inner layer and the surface layer will be different. will change. Therefore, there is a possibility that the dimensional accuracy of the cut out metal frame will be reduced.

In addition, the material 1 has a small difference in various physical properties between the inner layer portion and the surface layer portion (for example, a difference in cutting resistance to be described later).

As mentioned above, the homogeneity of the billet 1 is not only due to the fact that the billet 1 is made of a sintered body produced by powder metallurgy, but also due to the solid solution of N in the metal material from the powder manufacturing, and through The powder metallurgy method uses the powder to produce a sintered body. In order to solid-dissolve N in the metal material during powder production, a method of nitriding at least one of Co, Cr, Mo, and Si contained in the raw material can be used in advance, and the raw material can be kept molten in a nitrogen atmosphere during or after melting. The method of metal (molten metal), the method of injecting nitrogen gas (bubbling) into the molten metal, etc.

Furthermore, there is also a method of infiltrating N into the alloy body by heating a molded body obtained by molding metal powder or by sintering the sintered body in a nitrogen atmosphere, or by performing HIP treatment in a nitrogen atmosphere. Medium (nitrogenation treatment). However, with this method, it is difficult to uniformly nitride the molded body and the sintered body from the surface layer to the inner layer, and even if nitriding is possible, it takes a long time while suppressing the nitriding speed. It is problematic from an efficiency point of view.

In addition, when degreasing and firing a molded body in which N is solid-dissolved in the powder, the change in the concentration of solid-dissolved N can be suppressed by degreasing and firing in an inert gas such as nitrogen or argon.

In addition, it is considered that the ratio of the N content to the Si content (N/Si) affects the homogeneity of the billet 1 . That is, when N/Si is within the above range, the distortion of the crystal structure due to the solid solution of Si is suppressed by the solid solution of N, and as a result, it is considered that the homogeneity of the raw material 1 can be improved.

As described above, the raw material 1 is characterized in that the difference in cutting resistance between the surface layer portion and the inner layer portion is small. Therefore, it is possible to suppress a change in cutting resistance during the cutting process of the material 1 and to suppress a reduction in the dimensional accuracy of the cut out metal frame.

Specifically, for example, when the blank 1 is in the form of a plate with a thickness of 10 mm or more, the position from the surface to the depth of 0.3 mm in the section along the thickness direction of the blank 1 is taken as the surface layer part, and the position from the surface to the depth is 0.3 mm. The position of 5mm is used as the inner part.

In this case, the cutting resistance of the inner layer is preferably 50% to 200% of the cutting resistance of the surface layer, more preferably 60% to 175%, and still more preferably 75% to 150%. Accordingly, it is possible to suppress reduction in machining accuracy of the material 1 due to a change in cutting resistance. In addition, if the cutting resistance of the inner layer part is lower than the above-mentioned lower limit value, the difference between the cutting resistance of the inner layer part and the cutting resistance of the surface layer part will increase. Accuracy will be reduced. In other words, since the cutting resistance of the inner layer is much smaller than that of the surface layer, for example, when the processing tool in processing moves slowly from the surface layer to the inner layer, the cutting resistance becomes smaller, and it is possible that the driving force is closely related to the cutting force. The correlation between the results is out of balance, so that unwanted processing occurs. On the other hand, if the cutting resistance of the inner layer part is higher than the above-mentioned upper limit, similarly, depending on the positional relationship between the material 1 and the machining tool, machining accuracy may decrease. That is to say, the cutting resistance of the inner layer is much larger than that of the surface layer. For example, when the processing tool in processing moves slowly from the surface layer to the inner layer, the cutting resistance increases, and the driving force may be related to the cutting force. The correlation between the results is out of balance, so that unwanted processing occurs.

Furthermore, the material 1 is useful in that cutting resistance can be relatively suppressed not only in wet cutting but also in dry cutting. That is, the material 1 has a feature that the difference between the cutting resistance of wet cutting and the cutting resistance of dry cutting is small. Therefore, depending on the shape of the metal frame cut out from the blank 1, even with dry cutting, it is possible to cut out a metal frame with high dimensional accuracy.

Specifically, when the cutting resistance of wet cutting is 1, the cutting resistance of dry cutting is preferably 2 or less, more preferably 1.5 or less. As long as the cutting resistance of dry cutting is within the above range relative to the cutting resistance of wet cutting, a metal frame with high dimensional accuracy can be sufficiently cut out by dry cutting. Therefore, such a blank 1 can be easily It is useful for cutting.

Since the use of cutting fluid is not required by dry cutting, there is an advantage in that the man-hours for cleaning the cut metal frame can be saved. Especially when the metal frame is left in the body, it is necessary to avoid the residue of cutting fluid as much as possible. Therefore, dry cutting is also effective from the viewpoint of the safety of the cut metal frame.

In addition, in the wet cutting process of the material 1, good cutting results can be obtained even when a water-soluble cutting fluid is used instead of an oily cutting fluid. Since the water-soluble cutting fluid can be easily removed, the cleaning time can be controlled. Moreover, since good cutting results can be obtained even in the case of semi-dry cutting (MQL machining) that uses a small amount of cutting fluid, the amount of cutting fluid used can be significantly reduced, and at the same time, high dimensional accuracy can be cut. metal frame.

[Metal frame for dental porcelain]

Next, an embodiment of the dental metal frame for porcelain of the present invention will be described.

Fig. 7 is a perspective view showing a state in which an embodiment of the metal frame for dental ceramics of the present invention is cut out of the blank shown in Fig. 1 , and Fig. 8 is a sectional view taken along line A-A of Fig. 7 , Fig. 9 is a longitudinal sectional view showing an embodiment of the metal frame for dental porcelain of the present invention.

The cut blank 1' shown in Fig. 7 is a blank in which the metal frame 2 has been cut out by cutting the blank 1. The metal frame 2 is a member used as a base material for dental prostheses such as inlays, crowns, bridges, metal beds, dentures, implants, abutments, jigs, and screws. Thus, the approximate shape of the dental prosthesis can be determined from the metal frame 2, and the shape of the cut out metal frame 2 is therefore generally corresponding to the shape of the manufactured dental prosthesis. Then, by providing a ceramic material layer on the surface of the metal frame 2, a dental prosthesis described later can be obtained.

In addition, metal frames for ceramics are described here, but the metal frames of the present invention also include dental metal components not used for ceramics, such as inlays, crowns, bridges, metal beds, dentures, implants , Abutments, fixtures, screws and other dental metal components.

For the cutting process, any cutting machine can be used. For example, machining centers, milling machines, drilling machines, lathes, etc. Among them, it is preferable to use a cutting machine integrated into a CAM system. Using such a cutting machine can faithfully reflect a model obtained by a CAD system or the like on a machining result, and thus contributes to realization of a dental prosthesis that is particularly less uncomfortable to the patient.

The blank 1' after cutting shown in FIGS. 7 and 8 has a flat plate portion 3 made of the blank 1 and a metal cut out so as to be surrounded by a through hole 4 formed in the flat plate 3. frame 2. As shown in Fig. 8, between the metal frame 2 and the flat plate portion 3, there is a small connecting portion 5 connected, and finally by cutting the connecting portion 5, the metal frame 2 can be separated from the cut blank 1'.

The metal frame 2 shown in Fig. 9 shows a state in which the metal frame is separated from the cut blank 1' shown in Figs. 7 and 8 . In addition, the shape of the metal frame 2 shown in FIG. 9 is only an example, and the metal frame 2 can be formed into various shapes according to the type of dental prosthesis.

In addition, the obtained metal frame 2 may be subjected to grinding treatment as necessary. As the grinding treatment, for example, treatment methods such as barrel grinding and sand blasting may be mentioned.

Moreover, secondary processing can also be performed on the obtained metal frame 2 as required. Examples of secondary processing include mechanical processing such as cutting and grinding, laser processing, electron wire processing, water jet processing, electrical discharge processing, press processing, extrusion processing, rolling processing, forging processing, bending processing, drawing, etc. Deep processing, drawing processing, roll forming processing, shearing processing, etc.

As described above, the metal frame 2 obtained in this way has excellent machinability of the blank 1 and has high dimensional accuracy. This metal frame 2 will become a metal frame that can be installed on the affected part with less discomfort, and while reducing the burden on the patient as much as possible, as will be described later, when a ceramic material layer is provided on the surface of the metal frame 2, it can be used. A metal frame that realizes high adhesion and high aesthetics of the ceramic layer is obtained.

Furthermore, since the metal frame 2 has high corrosion resistance, it is a metal frame excellent in biocompatibility.

Furthermore, since the metal frame 2 has excellent mechanical properties and is hardly deformed by the occlusal force, it will be a metal frame excellent in durability.

In addition, after the metal frame 2 is separated from the cut blank 1', the remaining flat plate portion 3 can be used for cutting other metal frames 2, and can be recovered as a raw material for manufacturing a new blank 1. That is, the metal powder (the metal powder for powder metallurgy of the present invention) used in the production of the billet 1 can be obtained by melting the remaining flat plate portion 3 and pulverizing it by an atomization method or the like.

[Dental prosthetics]

Next, embodiments of the dental prosthesis of the present invention will be described.

Fig. 10 is a longitudinal sectional view showing an embodiment of the dental prosthesis of the present invention.

A dental prosthesis 10 shown in FIG. 10 includes a metal frame 2 and a ceramic material layer 6 provided to cover a part of its surface.

The ceramic material layer 6 is a part responsible for the aesthetics of the dental prosthesis 10, and generally exhibits a color close to the color of teeth.

Examples of the constituent material of the ceramic layer 6 include various ceramic materials such as feldspar, quartz, clay, and metal oxides, and various other resin materials. Among them, ceramic materials are preferably used from the viewpoints of aesthetics and adhesion to the metal frame 2 . Specifically, examples thereof include alumina, silica, lithium oxide, sodium oxide, potassium oxide, calcium oxide, iron oxide, magnesium, zirconia, titanium dioxide, antimony oxide, cerium oxide, etc., and one or more of them can be used. A mixture of two or more.

A paste including such a constituent material is applied to the surface of the metal frame 2, and then ceramic material layer 6 is formed by performing a ceramic treatment.

Among them, the constituent material of the ceramic material layer 6 preferably contains alumina. When a ceramic material including alumina is baked onto the surface of the metal frame 2 , a mullite phase is generated near the interface between the ceramic material layer 6 and the metal frame 2 . This mullite phase is generated by mixing alumina contained on the ceramic material side with Si or silicon oxide contained on the metal frame 2 side. Therefore, due to the mullite phase, the ceramic material layer 6 is tightly adhered to the metal frame 2, and the ceramic material layer 6 is difficult to peel off, so that a highly reliable dental prosthesis can be obtained. In addition, the generation of the mullite phase improves the wettability of the ceramic material to the metal frame 2 at the time of the porcelain firing process. Therefore, from this point of view, the adhesion of the ceramic material layer 6 is improved, and furthermore, the ceramic material layer 6 is not baked unevenly.

The content of alumina in the constituent materials of the ceramic layer 6 is preferably at least 2% by mass and at most 50% by mass, more preferably at least 4% by mass and at most 35% by mass, and even more preferably at least 35% by mass. More than 6% by mass and less than 25% by mass. By setting the alumina content within the above-mentioned range, it is possible to ensure sufficient alumina for improving the adhesion between the ceramic material layer 6 and the metal frame 2, and at the same time, the mechanical properties of the ceramic material layer 6 itself are improved. Therefore, a more reliable dental prosthesis 10 can be obtained.

Therefore, if the content of alumina is lower than the above-mentioned lower limit, a sufficient amount of mullite phase will not be generated between the ceramic material layer 6 and the metal frame 2, so the wettability of the ceramic material may be reduced. The adhesion of the ceramic material layer 6 will also be reduced. On the other hand, if the content of alumina exceeds the above-mentioned upper limit, the mechanical properties will be easily reduced, such as the ceramic material layer 6 will become brittle. Therefore, it may still cause The adhesiveness of the ceramic material layer 6 falls.

Furthermore, the average thickness of the ceramic material layer 6 is not particularly limited, but is preferably about 0.05 mm to 3 mm, more preferably about 0.2 mm to 2 mm. By setting the average thickness of the ceramic material layer 6 within the above range, the adhesion of the ceramic material layer 6 to the metal frame 2 can be further improved. Furthermore, since the ceramic material layer 6 is provided with necessary and sufficient light-shielding properties, the color of the metal frame 2 is less likely to be transparent, and a dental prosthesis excellent in aesthetics can be obtained.

When forming the ceramic material layer 6 , first, the constituent materials of the ceramic material layer 6 are pulverized using a planetary mill, a ball mill, or the like. Then, heat treatment is performed in a range of from 800° C. to 1100° C. for 30 minutes to 60 minutes as necessary.

The pulverized product thus obtained is dispersed in a dispersant to prepare a paste or slurry. In this way, the paste and slurry required for forming the ceramic material layer 6 can be obtained. Examples of the dispersant include water, propylene glycol, ethylene glycol, glycerin, polymethyl methacrylate, polyvinyl acetate, nitrocellulose, ethyl cellulose and the like.

The obtained paste and paste are coated on the surface of the metal frame 2, and the porcelain-fired treatment is performed. The firing temperature can be appropriately set according to the constituent materials of the ceramic material layer 6, for example, it is set at 500°C or more and 1000°C or less. In this way, a dental prosthesis 10 is obtained.

As mentioned above, through the preferred embodiment, the blank material to be machined for dental use, the metal powder for powder metallurgy, the metal frame for dental ceramics, and the dental prosthesis have been described, but the present invention is not limited to this.

For example, in the above-mentioned embodiment, the case where a plurality of metal frames for dental ceramics are cut out from the blank to be machined for dentistry has been described, but the present invention is not limited to this case, and can also be applied In the case of cutting a metal frame from a billet.

【Example】

Next, specific examples of the present invention will be described.

1. Manufacture of blanks for dental machining

(Sampling No.1)

[1] First, the raw material is melted in a high-frequency induction furnace and powdered by the water atomization method to obtain metal powder. Next, classification was performed using a standard sieve with an opening of 150 μm. The alloy composition of the obtained metal powder is shown in Table 1. In addition, N is contained in the raw material in a state bonded to Cr (state of chromium nitride). In addition, in specifying the alloy composition, a solid-state emission spectrometer (spark emission spectrometer) manufactured by SPECTRO Corporation, model: SPECTROLAB, type: LAVMB08A was used. In addition, the quantitative analysis of C (carbon) used CS-200 carbon-sulfur analyzer manufactured by LECO company.

[2] Next, the obtained organic binder is dissolved in water to prepare a binder solution. In addition, the amount of the organic binder in the binder solution was 10 g per 1 kg of metal powder. In addition, the amount of water in the binder solution was 50 g per 1 g of the organic binder.

[3] Next, the metal powder is put into the processing container of the granulation device. Then, while spraying the binder solution onto the metal powder in the processing container from the spray nozzle of the granulator, the metal powder is granulated by a spray drying method to obtain a granulated powder.

[4] Next, using the obtained granulated powder, molding was performed under the following molding conditions to obtain a molded body.

<Molding conditions>

·Molding method: pressed powder molding

·Molding pressure: 300MPa (3t/cm ² )

[5] Next, the molded body was degreased according to the following degreasing conditions to obtain a degreased body.

<Conditions for degreasing>

·Heating temperature: 470℃

·Heating time: 1 hour

· Heating atmosphere: nitrogen atmosphere

[6] Next, the obtained degreased body was fired under the following firing conditions to obtain a sintered body (material for dental machining). The obtained dental material to be machined was in the shape of a disc with a diameter of 100 mm and a thickness of 15 mm.

<Firing conditions>

·Heating temperature: 1300℃

·Heating time: 3 hours

Heating atmosphere: argon atmosphere

(Sampling No.2～No.16)

Except that the manufacturing conditions were set to the conditions shown in Table 1, the rest were the same as the case of sampling No. 1, thereby obtaining dental blanks for machining.

(Sampling No.17～No.20)

When melting raw materials in a high-frequency induction furnace, nitrogen gas is injected into the molten metal. At this time, by appropriately changing the injection time, the N content was changed.

In addition, except that the other manufacturing conditions are as shown in Table 1, the rest were the same as the case of sample No. 1, thereby obtaining a dental blank to be machined.

(Sampling No.21～No.24)

First, metal powders were obtained in the same manner as in the case of sample No. 1 using a raw material not containing N.

Next, except that while using this metal powder, the heating atmosphere of the firing conditions was changed to a mixed gas atmosphere of 50% by volume of argon and 50% by volume of nitrogen, the rest were the same as the sampling No. 1, a sintered body was obtained. At this time, by appropriately changing the partial pressure of nitrogen, the content of N contained in the metal powder was changed.

In addition, except that the other manufacturing conditions are as shown in Table 1, the rest were the same as the case of sample No. 1, thereby obtaining a dental blank to be machined.

(Sampling No.25, No.26)

When melting raw materials in a high-frequency induction furnace, nitrogen gas is injected into the molten metal. At this time, by appropriately changing the injection time, the content of N contained in the metal powder is changed.

In addition, except that the other manufacturing conditions are as shown in Table 1, the rest were the same as the case of sample No. 1, thereby obtaining a dental blank to be machined.

(Sampling No.27～No.29)

When melting raw materials in a high-frequency induction furnace, nitrogen gas is injected into the molten metal, and then the molten metal is poured into a mold in the shape of a billet to obtain a cast body. At this time, by appropriately changing the injection time, the content of N contained in the metal powder is changed.

In addition, except that the other manufacturing conditions are as shown in Table 1, the rest were the same as the case of sample No. 1, thereby obtaining a dental blank to be machined.

Tables 1 and 2 show the manufacturing conditions of the dental workpiece blanks for each sampling No. mentioned above.

Table 1

Table 2

In addition, in each table, among the metal powders of each sample No. and the material to be machined for dental use, those samples corresponding to the present invention are expressed as "Example", and those samples not in accordance with the present invention are expressed as "Example". , expressed as a "comparative example".

2. Evaluation of raw materials for dental machining

2.1 Measurement of the Si content contained as the total amount of Si and silicon oxide

The content of Si contained as the total amount of Si and silicon oxide was measured by the gravimetric method and the ICP emission spectrometry for each sample No. of the dental workpiece material. The measurement results are shown in Table 3.

2.2 Evaluation of crystal structure by X-ray diffraction method

The crystal structure analysis by the X-ray diffraction method was performed on the dental workpiece material of each sampling No. Then, the crystal structure contained in the blank was identified by comparing the height and position of each peak included in the obtained X-ray diffraction pattern with the database registered in the ICDD card. Furthermore, assuming that the height of the highest peak among the peaks derived from Co was 1, the ratio of the heights of the highest peak among the peaks derived from Co ₃ Mo was calculated. The calculation results are shown in Table 3.

2.3 Evaluation of aspect ratio of pores, dendrite phase and crystal structure

A test piece was cut out from the dental material to be machined for each sampling No. by cutting.

Next, the cut surface of the test piece was ground. Then, the polished surface was observed using a scanning electron microscope, and the region occupied by the voids was identified on the observation image. Then, the average diameter of the area occupied by the measured voids was calculated (regarded as the average diameter of the voids), and the ratio of the area of the area occupied by the voids to the total area of the observed image (area ratio) was calculated.

Then, the degree of presence of the dendrite phase was evaluated in accordance with the following evaluation criteria by confirming how much the dendrite structure existed in the observation image.

<Evaluation Criteria for Dendritic Phase>

◎: There is almost no dendrite phase

○: Some dendrite phases exist (area ratio is 10% or less)

△: There are slightly more dendrite phases (the area ratio is 10% or more and 20% or less)

×: There are very many dendrite phases (area ratio exceeds 20%)

Then, the obtained polished surface was observed with a scanning electron microscope, and the average value of the aspect ratio of the crystal structure on the observed image was calculated.

The above evaluation results are shown in Table 3.

2.4 Evaluation of N concentration

The dental material to be machined for each sampling No. was cut in the thickness direction, and the cut surface was ground.

Next, on the ground surface, a line analysis of the blank from the surface to the inside was carried out using an electron beam analyzer (EPMA). Furthermore, the concentration distribution of N in the thickness direction of the billet was obtained.

Next, the N concentration from the surface to the position of 0.3 mm is taken as the N concentration of the surface layer, and the N concentration from the surface to the position of 5 mm is taken as the N concentration of the inner layer, and the N concentration of the inner layer is calculated for the N concentration of the surface layer. ratio of N concentration. The calculation results are shown in Table 3.

2.5 Determination of Vickers hardness

Dental material to be machined for each sample No. was cut in the thickness direction, and the cut surface was ground.

Next, the Vickers hardness was measured at a position from the surface of the billet to 0.3 mm in the polished surface, and this was defined as the Vickers hardness of the surface layer. And the Vickers hardness was measured from the surface of the billet to the position of 5 mm, and this was made into the Vickers hardness of an inner layer part.

Next, the ratio of the Vickers hardness of the inner layer portion to the Vickers hardness of the surface layer portion was obtained. The calculation results are shown in Table 3.

In addition, the measured values of the Vickers hardness of the surface layer are shown in Table 4.

In addition, the test load of the diamond indenter was 100 gf.

2.6 Evaluation of corrosion resistance

A test piece was cut out from the dental material to be machined for each sampling No. by cutting.

Next, the amount of eluted metal ions was measured for the obtained test pieces in accordance with the test method for corrosion resistance of precious metal materials for dental metal-ceramic restorations specified in JIS T 6118 (2012).

Then, the results of the measurement were evaluated according to the following evaluation criteria.

<Evaluation criteria for corrosion resistance>

◎: Very strong corrosion resistance (very little elution of metal ions)

○: Strong corrosion resistance (less elution of metal ions)

△: Weak corrosion resistance (a large amount of elution of metal ions)

×: Corrosion resistance is very weak (the amount of elution of metal ions is very large)

The above evaluation results are shown in Table 4.

2.7 Determination of 0.2% endurance, elongation and Young's modulus

A test piece was cut out from the dental material to be machined for each sampling No. by cutting.

Next, the obtained test pieces were measured for 0.2% proof strength, elongation and Young's modulus in accordance with the test method for mechanical properties of precious metal materials for dental metal-ceramic restorations specified in JIS T 6118 (2012).

Furthermore, the Young's modulus was obtained in accordance with the test method for dental metal materials specified in JIS T 6004 (2012).

The measurement results are shown in Table 4.

2.8 Determination of fatigue strength

A test piece was cut out from the dental material to be machined for each sampling No. by cutting.

Next, the fatigue strength of the obtained test pieces was measured according to the test method specified in JIS T 0309 (2009).

The measurement results are shown in Table 4.

2.9 Machinability evaluation

2.9.1 Evaluation based on chip length

Machinability was evaluated for each sample No. of the dental workpiece to be machined as described below.

First, holes are cut into the obtained billet using a drill. Next, chips generated during the cutting process were recovered, and their average lengths were measured. Then, the average length of the measured chips was evaluated according to the following evaluation criteria. In addition, the cutting process uses a cemented carbide drill with a diameter of 2 mm at a speed of 420 revolutions per minute. Also, no cutting oil is used.

<Evaluation Criteria for Machinability>

◎: The average length of chips is less than 5mm (excellent machinability)

〇: The average length of chips is 5 mm or more and less than 10 mm (good machinability)

△: The average length of chips is 10 mm or more (slightly poor machinability)

×: Chips with an average length of 10 mm or more and chips in a spiral shape (poor machinability)

The above evaluation results are shown in Table 4.

2.9.2 Evaluation based on cutting resistance

The cutting resistance was evaluated for the dental blanks to be machined obtained in each of the Examples and each of the Comparative Examples as follows.

First, the obtained billet was fixed to the measurement section of the three-component cutting force gauge.

Next, the surface layer portion of the blank was cut using the machining center so that the machining tool was scanned along the trajectory shown in FIG. 6 . Then, the maximum value was obtained from the cutting resistance of the three components measured during the cutting process, and evaluated according to the following evaluation criteria.

<Evaluation criteria for cutting resistance>

◎: Cutting resistance is 200N or less.

〇: Cutting resistance is not less than 200N and not more than 250N.

Δ: Cutting resistance is not less than 250N and not more than 300N.

×: Cutting resistance is 300N or more.

The above evaluation results are shown in Table 4.

On the other hand, the machining center was used to cut the inner layer portion of the material so that the machining tool was scanned along the trajectory shown in FIG. 6 . Then, the maximum value was obtained from the cutting resistance of the three components measured during the cutting process.

Next, the ratio of the cutting resistance of the inner layer part to the cutting resistance of the surface layer part obtained earlier is calculated. The calculation results are shown in Table 4.

2.10 Evaluation of thermal expansion coefficient

A test piece was cut out from the dental material to be machined for each sampling No. by cutting.

Next, the temperature dependence of thermal expansion was determined for the obtained test piece according to the test method specified in JIS Z 2285 (2003). At this time, by repeating the rise and fall of the temperature, the stability of the temperature dependence of thermal expansion, that is, the stability of the thermal expansion coefficient was confirmed. Then, the stability of the coefficient of thermal expansion was evaluated according to the following evaluation criteria.

<Evaluation Criteria for Stability of Thermal Expansion Coefficient>

◎: The coefficient of thermal expansion is particularly stable.

〇: The coefficient of thermal expansion is stable.

Δ: The coefficient of thermal expansion is slightly unstable.

×: The coefficient of thermal expansion is unstable.

The evaluation results are shown in Table 4.

table 3

Table 4

As can be seen from Table 3 and Table 4, the dental blanks to be machined corresponding to the respective examples are excellent in corrosion resistance. Furthermore, it is considered that the Vickers hardness is appropriate, and the 0.2% proof strength, elongation, and Young's modulus are large.

Furthermore, it is considered that the difference in N concentration and the difference in hardness between the inner layer portion and the surface layer portion are small.

Moreover, due to its excellent machinability, smooth cutting can be performed with small cutting resistance during cutting, and the change in cutting resistance is small, so desired shapes can be effectively cut out. In addition, since the difference in cutting resistance observed between the inner layer part and the surface layer part is sufficiently small, from this point of view, it can be considered that the dental blanks to be machined obtained by each Example can effectively cut out the desired shape.

Furthermore, it is considered that the dental workpiece materials corresponding to the respective examples contain a certain amount of silicon oxide and voids, and contain almost no dendrite phase.

On the other hand, it can also be seen that the corrosion resistance, mechanical properties, and machinability of the dental blanks to be machined corresponding to the respective comparative examples are all low.

3. Manufacture of dental prostheses

By cutting, test pieces were cut out from the raw material to be machined for dentistry of each sampling No. .

Next, the paste of opaque porcelain was coated on the surface of the obtained test piece and fired. Thus, a test piece of a dental prosthesis was obtained.

In addition, as the paste (alumina content: 15% by mass) of opaque porcelain, "Retro MP" manufactured by Matsukaze Co., Ltd. was used. Also, the firing temperature was set at 950° C., and kept at this temperature for 2 minutes. In addition, the firing atmosphere was set to be a reduced-pressure atmosphere.

4. Evaluation of Dental Prosthesis

For the test pieces of dental prosthesis obtained by firing opaque porcelain on the test pieces cut out from the blanks of each sampling No., the peeling of dental metal-ceramic restorations specified in JIS T 6120 (2001) The adhesiveness of the ceramic layer was also evaluated according to the following evaluation criteria while applying a destructive force to the crack occurrence strength test.

<Evaluation Criteria for Peeling/Cracking Incidence Strength Test>

⊚: 2 times or more that of the test piece obtained by sampling the billet of No. 27.

〇: 1.5 times or more and 2 times or more of the test piece obtained by sampling the raw material of No. 27.

Δ: 1 to 1.5 times that of the test piece obtained by sampling the material of No. 27.

x: 1 time or less of the test piece obtained by sampling the raw material of No. 27.

As can be seen from Table 4, compared with the dental prosthesis corresponding to each example, the adhesiveness of the ceramic material layer of the dental prosthesis corresponding to each example is higher.

Furthermore, the dental prosthesis corresponding to each Example was cut, and the surface analysis was performed on the cross-section by an electron beam analyzer. As a result, it was found that a layered mullite phase existed at the interface between the ceramic layer and the metal frame.

Furthermore, the material corresponding to each Example was subjected to HIP treatment under the following conditions.

<HIP processing conditions>

·Heating temperature: 1100℃

·Heating time: 2 hours

·Adding pressure: 100MPa

Next, as in 2.9 above, machinability evaluation was performed on the HIP-treated billet. As a result, the machinability of the HIP-treated billet was slightly lower than that of the non-HIP-treated billet. The detailed reason is not clear, but as one of the reasons, for example, the hardness of the billet increases with the HIP treatment.

5. Evaluation of the relationship between N concentration and hardness

First, dental workpiece blanks of Sample Nos. 30 to 36 having the alloy compositions shown in Table 5 were prepared.

Next, the Vickers hardness of the surface layer part and the inner layer part of each sample Nos. 30 to 36 of the dental workpiece to be machined was measured according to the above-mentioned "2.5 Measurement of Vickers hardness". The measurement results are shown in Table 5 and Figure 11.

table 5

It can be seen from Table 5 and Figure 11 that there is a very small correlation between the N concentration in the billet and the Vickers hardness at a specific N concentration. As described above, the hardness decreases, so the toughness of the billet increases, so that the tensile strength, endurance, etc. can be improved. Furthermore, from the N concentration measurement results, it can be seen that even if the total N concentration is changed, there is no significant difference in N concentration between the surface layer part and the inner layer part.

Symbol Description

1. 1’ Dental blank to be machined 2 Metal frame

3 Flat part 4 Through hole

5 Connecting part 6 Ceramic layer

7 Three-component cutting force tester 71 Measurement department

72 Fixing part 73 Processing tool

74 sets of 10 dental restorations

11 upper surface 12 lower surface

TR track.

Claims (16)

1. A dental blank to be machined, characterized in that, Co is the principal component, Containing Cr in a ratio of 26% by mass to 35% by mass, Mo is contained in a ratio of not less than 5% by mass and not more than 12% by mass, Si is contained in a ratio of 0.3% by mass to 2.0% by mass, Containing N in a ratio of 0.09% to 0.5% by mass, The dental material to be machined is composed of a sintered body of metal powder, and, Wherein the dental blank to be machined includes a surface layer part and an inner layer part, and In the cross-section of the dental blank to be processed, when the position from the surface to a depth of 0.3 mm is defined as the surface portion, and the position from the surface to a depth of 5 mm is defined as the inner portion, the inner portion The N concentration in the layer portion is not less than 50% and not more than 200% of the N concentration in the surface layer portion. 2. The dental blank to be machined according to claim 1, wherein: In the cross-section of the dental blank to be processed, when the position from the surface to the depth of 0.3 mm is defined as the surface portion, and the position from the surface to the depth of 5 mm is defined as the inner portion, The Vickers hardness of the inner layer part is 67% or more and 150% or less of the Vickers hardness of the surface layer part. 3. The dental blank to be machined according to claim 1, wherein: The Vickers hardness of the inner layer part is not less than 200 and not more than 480. 4. The dental blank to be machined according to claim 1, wherein: The ratio of the N content to the Si content is 0.1 to 0.8. 5. The dental blank to be machined according to claim 1, wherein: Part of the Si is contained as silicon oxide, The ratio of Si contained as the silicon oxide in the Si is not less than 10% by mass and not more than 90% by mass. 6. The dental blank to be machined according to any one of claims 1 to 3, wherein: Part of the Si is contained as silicon oxide, The ratio of Si contained as the silicon oxide in the Si is not less than 10% by mass and not more than 90% by mass, The silicon oxide is segregated at the grain boundaries of the sintered body. 7. The dental blank to be machined according to claim 1, wherein: In the X-ray diffraction pattern obtained by the X-ray diffraction method using the CuKα line, when the height of the highest peak among the peaks derived from Co determined based on the quasi-diffraction data card is set to 1, the peak due to the determination based on the quasi-diffraction data card is 1. The ratio of the height of the highest peak among the peaks of Co ₃ Mo is not less than 0.01 and not more than 0.5. 8. The dental material to be machined according to claim 1, wherein: The dental material to be machined has a 0.2% proof strength of 450 MPa or more, an elongation of 2% or more, and a Young's modulus of 150 GPa or more. 9. A metal powder for powder metallurgy, characterized in that, Co is the principal component, Containing Cr in a ratio of 26% by mass to 35% by mass, Mo is contained in a ratio of not less than 5% by mass and not more than 12% by mass, Si is contained in a ratio of 0.3% by mass to 2.0% by mass, Containing N in a ratio of 0.09% to 0.5% by mass, The metal powder for powder metallurgy is used in the manufacture of machined billets for dental use, and The ratio of Si contained as silicon oxide in the above-mentioned Si is 10% by mass or more and 90% by mass or less. 10. The metal powder for powder metallurgy according to claim 9, characterized in that, The content of Co is not less than 50% by mass and not more than 67.5% by mass. 11. The metal powder for powder metallurgy according to claim 9, characterized in that, A ratio of the N content to the Si content is 0.1 to 0.8. 12. The metal powder for powder metallurgy according to any one of claims 9 to 11, characterized in that, Part of the Si is contained as silicon oxide, The ratio of Si contained as the silicon oxide in the Si is not less than 10% by mass and not more than 90% by mass, The silicon oxide is segregated at the grain boundaries of the sintered body. 13. The metal powder for powder metallurgy according to claim 9, characterized in that, In the X-ray diffraction pattern obtained by the X-ray diffraction method using the CuKα line, when the height of the highest peak among the peaks derived from Co determined based on the quasi-diffraction data card is set to 1, the peak due to the determination based on the quasi-diffraction data card is 1. The ratio of the height of the highest peak among the peaks of Co ₃ Mo is not less than 0.01 and not more than 0.5. 14. A metal frame for dental porcelain, characterized in that, Co is the principal component, Containing Cr in a ratio of 26% by mass to 35% by mass, Mo is contained in a ratio of not less than 5% by mass and not more than 12% by mass, Si is contained in a ratio of 0.3% by mass to 2.0% by mass, Containing N in a ratio of 0.09% to 0.5% by mass, The dental metal frame for ceramics is obtained by cutting a dental machined blank made of a sintered body of metal powder, and The ratio of Si contained as silicon oxide in the Si is not less than 10% by mass and not more than 90% by mass. 15. A dental prosthesis, characterized in that it has: The metal frame for dental porcelain porcelain according to claim 14; and The ceramic material layer is arranged on the surface of the metal frame for dental ceramics. 16. Dental prosthesis according to claim 15, characterized in that, The ceramic layer comprises alumina, The dental prosthesis also has a mullite phase between the dental ceramic metal frame and the ceramic layer.